Simultaneous Regasification of Liquefied Natural Gas and Desalination

Abstract

A process and apparatus is presented for the desalination of water by freezing seawater. The process is integrated into a liquefied natural gas regasification system. The process comprises alternating the flow of liquefied natural gas to freeze seawater in a heat exchanger and then flowing a hot flue gas through the heat exchanger to melt the frozen seawater, and then repeating the process.

1 . A process for desalinating seawater comprising:
 a) flowing a portion of a liquefied natural gas stream through a first side of a first heat exchanger;   b) flowing seawater through a second side of the first heat exchanger thereby forming ice in the second side of the heat exchanger;   c) stopping the flow of the liquefied natural gas into the heat exchanger;   d) stopping the flow of seawater into the heat exchanger and draining residual amounts of seawater from the heat exchanger;   e) passing hot combusted flue gas stream through the first side of the heat exchanger, thereby melting the ice in the second side of the heat exchanger creating fresh water;   f) draining the fresh water from the second side of the heat exchanger; and   g) repeating steps a through f.   
   
   
       2 . The process of  claim 1  further comprising:
 passing a second portion of the liquefied natural gas stream to a combustor;   passing a compressed air stream to the combustor;   combusting the natural gas and air, thereby forming a hot combusted gas stream;   passing the hot combusted gas stream to a turbine expander, thereby generating power and forming the hot combusted flue gas stream.   
   
   
       3 . The process of  claim 2  further comprising:
 passing a portion of the liquefied natural gas stream through a first side of a second heat exchanger; and   passing an air stream through a second side of the second heat exchanger, thereby creating a cooled air stream, and an intermediate liquefied natural gas stream, wherein the intermediate liquefied natural gas stream is passed to the first heat exchanger.   
   
   
       4 . The process of  claim 3  further comprising passing the cooled air stream to a compressor, thereby forming the compressed air stream. 
   
   
       5 . The process of  claim 2  further comprising:
 passing the second portion of the liquefied natural gas stream through a first side of a third heat exchanger;   passing the hot combusted flue gas stream through the second side of the third heat exchanger, thereby vaporizing a portion of the second portion of the liquefied natural gas stream.